The present invention relates to enhancing the conductivity of subterranean formations while controlling proppant flowback. More particularly, the present invention relates to improved resin compositions and resin-coated proppants and their use in controlling proppant flowback
Hydrocarbon-producing wells are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous fracturing fluid, which also functions as a carrier fluid, is pumped into a producing zone to be fractured at a rate and pressure such that one or more fractures are formed in the zone. Particulate solids for propping the fractures, commonly referred to in the art as “proppant,” are generally suspended in at least a portion of the fracturing fluid so that the particulate solids are deposited in the fractures when the fracturing fluid reverts to a thin fluid to be returned to the surface. The proppant deposited in the fractures functions to prevents the fractures from fully closing and maintains conductive channels through which produced hydrocarbons can flow.
In order to prevent the subsequent flowback of proppant and other unconsolidated particulates with the produced fluids a portion of the proppant introduced into the fractures may be coated with a hardenable resin composition. When the fracturing fluid, which is the carrier fluid for the proppant, reverts to a thin fluid the resin-coated proppant is deposited in the fracture, and the fracture closes on the proppant. Such partially closed fractures apply pressure on the resin-coated proppant particles, causing the particles to be forced into contact with each other while the resin composition hardens. The hardening of the resin composition under pressure brings about the consolidation of the resin-coated proppant particles into a hard permeable mass having compressive and tensile strength that hopefully prevents unconsolidated proppant and formation sand from flowing out of the fractures with produced fluids. Flowback of the proppant or formation fines with formation fluids is undesirable as it may erode metal equipment, plug piping and vessels, and cause damage to valves, instruments, and other production equipment.
Using heretofore known hardenable resin compositions has been disadvantageous because they have short shelf lives. That is, the shelf lives of the hardenable resin components, once mixed, have heretofore been as short as about four hours or less. It has been a common practice to utilize proppant that is pre-coated with a resin composition. However, such pre-coated resins generally begin to cure immediately after they are mixed and coated onto the proppant so that by the time the proppant is used, the resin may be more than 90% cured. When such pre-cured resin completes curing once placed in the subterranean formation, the resulting consolidated proppant pack often does not have enough strength to prevent deterioration of the proppant pack and proppant flowback.